Temperatures

In the atmosphere, 500-millibar height pressure anomalies correlate well with temperatures at the Earth's surface. The average position of the upper-level ridges of high pressure and troughs of low pressure—depicted by positive and negative 500-millibar height anomalies on the January 2015 map—is generally reflected by areas of positive and negative temperature anomalies at the surface, respectively.

January

The January 2015 globally-averaged temperature across land and ocean surfaces was 0.77°C (1.39°F) above the 20th century average of 12.0°C (53.6°F), the second highest on record for January since records began in 1880. The warmest January was in 2007, when the monthly global temperature was 0.86°C (1.55°F) above average.

The global land surface temperature was 1.43°C (2.57°F) above average, also the second highest on record for January behind 2007. The Northern Hemisphere was third warmest for the month over land, while the Southern Hemisphere had its 19th highest January land temperature in the 136-year period of record. Across the globe, much warmer-than-average temperatures were observed across much of central to eastern Asia, much of Europe, parts of western North America and southern North America stretching through Central America into northern and eastern South America, according to the January Land & Ocean Temperatures Departure from Average and Percentiles maps above. Some areas in southern Siberia and Far East Russia were more than 5°C (9°F) warmer than their long-term (1981–2010) monthly averages. Cooler-than-average conditions were notable across part of northern Australia, eastern Canada, and small regions of southern North America. A part of the Northern Territory in Australia was much below average during the month, the only land area around the globe with this distinction.

Select national information is highlighted below:

China observed its warmest January since national records began in 1961, at 1.9°C (3.4°F) above the 1981–2010 average.

Austria reported its 17th warmest January in its 248-year period of record, at 2.7°C (4.9°F) above the 1981–2010 average. The east saw the highest departures from average, reaching up to +3.8°C (+6.8°F).

In Norway the average temperature was 2.6°C (4.7°F) above the 1961–1990 average. Some regions in the eastern part of the country had departures 5–7°C (9–11°F) higher than average.

It was a bit cooler than average in Spain during January, with a temperature 0.4°C (0.7°F) below the 1981–2010 average.

For the oceans, the globally-averaged temperature anomaly of +0.53°C (+0.95°F) was the third highest on record for January in the 136-year period of record. In the midst of a strong El Niño, 1998 had the highest January global ocean temperature on record at +0.56°C (+1.01°F), while 2010, also in the midst of an El Niño, had the second highest. In January 2015, for the 33rd straight month, ENSO-neutral conditions persisted in the eastern and central equatorial Pacific Ocean. According to NOAA's Climate Prediction Center, as of early February 2015 there is about a 50–60 percent chance of a weak El Niño within the late Northern Hemisphere winter into early spring, with neutral conditions slightly favored thereafter.

During January 2015, record warmth was observed in part of the Gulf of Alaska, the eastern Pacific off the coastal United States, regions of the equatorial western Pacific and the Pacific waters to the east of Australia, large areas of the western Atlantic and some isolated regions of the eastern Atlantic near the southwestern African coast, along with the seas to the northeast of Iceland and above northern Europe. Parts of the southeastern Pacific, the Southern Ocean near the tip of South America, and part of the Atlantic Ocean between Canada and Europe were much cooler than average, with an area of the latter observing record cold sea surface temperatures. Overall, however, the scattered regions of record warmth combined with many areas that were much warmer than average led to the warmest January sea surface temperatures on record for the Northern Hemisphere, surpassing the previous record set (and tied) in 1998, 2007, and 2010 by 0.06°C (0.11°F).